Originally Posted by khuon

You really have to put a bit of force on the Specialized "nipples" of my bottles in order for them to open up. They're rubber and not plastic. This can actually be kind of annoying (although not terribly so) when you're trying to take a quick drink on the bike but I've never had the top just pop-open. It's not like one of those cheap bottles of water you get at the grocery store. It requires quite a tug.